(function() {

        // Private array of chars to use
        var CHARS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('');

        Math.uuid = function(len, radix) {
            var chars = CHARS,
                uuid = [],
                i;
            radix = radix || chars.length;

            if (len) {
                // Compact form
                for (i = 0; i < len; i++) uuid[i] = chars[0 | Math.random() * radix];
            } else {
                // rfc4122, version 4 form
                var r;

                // rfc4122 requires these characters
                uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
                uuid[14] = '4';

                // Fill in random data.  At i==19 set the high bits of clock sequence as
                // per rfc4122, sec. 4.1.5
                for (i = 0; i < 36; i++) {
                    if (!uuid[i]) {
                        r = 0 | Math.random() * 16;
                        uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];
                    }
                }
            }

            return uuid.join('');
        };

        // A more performant, but slightly bulkier, RFC4122v4 solution.  We boost performance
        // by minimizing calls to random()
        Math.uuidFast = function() {
            var chars = CHARS,
                uuid = new Array(36),
                rnd = 0,
                r;
            for (var i = 0; i < 36; i++) {
                if (i == 8 || i == 13 || i == 18 || i == 23) {
                    uuid[i] = '-';
                } else if (i == 14) {
                    uuid[i] = '4';
                } else {
                    if (rnd <= 0x02) rnd = 0x2000000 + (Math.random() * 0x1000000) | 0;
                    r = rnd & 0xf;
                    rnd = rnd >> 4;
                    uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];
                }
            }
            return uuid.join('');
        };

        // A more compact, but less performant, RFC4122v4 solution:
        Math.uuidCompact = function() {
            return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
                var r = Math.random() * 16 | 0,
                    v = c == 'x' ? r : (r & 0x3 | 0x8);
                return v.toString(16);
            });
        };
    })();